1. Field
The present invention relates generally to wireless communications, and more particularly to link control in wireless communications.
2. Background
The increased demand for wireless resources to carry voice and data messages sometimes results in an increase in transmission errors due to competing signals being simultaneously transmitted. Transmission errors are also caused by inclement weather, signal strength shadows, electrical interference or other conditions affecting the air interface, resulting in one or more packets in a wireless communication being dropped or corrupted. When a dropped or corrupted packet occurs, additional wireless system resources are typically needed to retransmit the lost data.
FIGS. 1A and 1B depict a conventional scheme for recovering dropped or corrupted wireless packets in W-CDMA. The figures illustrate a typical timing relationship at the receiver between polls 120 received from the sender, dropped packets 101-105, status reports including NAKs (negative acknowledgments) 131-133, status-prohibit timers 141-143, and retransmitted packets 111-115. FIG. 1A shows the various signals 101-120 received at a receiver, while FIG. 1B shows NAKs 131-133 and retransmissions 111-115 being sent between the receiver and the sender. Slots 101-105 represent corrupted packets at the receiver.
Upon determining that packet 101 is corrupted, the receiver transmits back to the sender a status report which includes NAK 131 instructing the sender to initiate a retransmission of the corrupted packet 101. Conventional W-CDMA status reports typically have a requirement to include NAKs for all pending sequence number gaps that exist since the latest in-sequence received sequence number. This need to include all pending sequence number gaps in conventional status reports wastes valuable wireless resources. For example, wireless resources are wasted when a status report is sent back to the sender with NAKs for corrupted packets which are already in the process of being retransmitted, resulting in a second, unnecessary spurious retransmission from the sender.
To avoid triggering spurious retransmissions and wasting valuable wireless bandwidth, W-CDMA introduced a status-prohibit mechanism, the status-prohibit timers 141-143. A general status-prohibit timer is started as soon as any status report is sent out. Presently, W-CDMA requires that once the status-prohibit timer is started, no further status reports are transmitted until the timer runs out. Any polls received from the sender while a status-prohibit timer is running are delayed until the timer runs out. Upon detecting a corrupted packet the status report with the NAK for the corrupted packet is delayed until the pending status-prohibit timer expires.
In FIG. 1, as soon as the status report including NAK 131 is sent from the receiver, the status-prohibit timer 141 is started, which prevents the transmission of any further status reports until it expires. Thus, when corrupted packet 102 is detected (while status-prohibit timer 141 is still running), the status report with NAK 132 for corrupted packet 102 is delayed until status-prohibit timer 141 has timed out. By the time status prohibit timer 141 has timed out, the retransmission for corrupted packet 101 has been received at the receiver as retransmitted packet 111, as shown in FIGS. 1A and 1B. Once status-prohibit timer 141 has expired the receiver can send another status report which includes NAK 132 requesting a retransmission of corrupted packet 102, previously detected while status-prohibit timer 141 was still running.
The present invention is directed to overcoming, or at least reducing the effects of, one or more problems indicated above.